The present invention relates to a fluid control valve with butterfly-type flow control element with high operating reliability.
It is known that fluid control valves with a butterfly-type flow control element are generally constituted by a valve body which is formed monolithically and is crossed by a passage which has, on the valve body, an inlet and an outlet which can be connected to the two branches of a duct for a fluid to be controlled by means of the valve. The valve body accommodates, in an intermediate region of the passage, a butterfly-type flow control element which can be actuated in order to open or close the passage.
In some valves, in an intermediate region of the passage the valve body supports an annular gasket which is fixed to the valve body and can be engaged by the flow control element when it is moved into the closure position.
In these valves, the annular gasket is coupled to a circumferential protrusion of the valve body which lies inside the passage and has, in radial cross-section, a dovetail profile.
In these valves, the connection between the annular gasket and the valve body reduces the actual passage section for the fluid, owing to the fact that the annular gasket necessarily protrudes inside the fluid passage. Moreover, in order to give the annular gasket a rigidity which ensures the required seal when the butterfly-type flow control element is moved into the closure position, a metal core is provided inside the annular gasket. The presence of the metal core has the drawback that it requires a considerable force in order to close the valve, since it reduces the deformability of the annular gasket and therefore contrasts, with a strong force, the final closure movement and the initial opening movement of the flow control element, i.e., when the flow control element is in contact with the annular gasket.
In order to solve the problem of an excessive reduction of the passage for the fluid inside the valve body, in some valves, particularly in valves designed to be fitted on ducts having a small cross-section, the body is formed in two parts so as to be able to have a duct which has a larger cross-section at the region occupied by the butterfly-type flow control element. Although these valves solve the problem of fluid passage reduction, they still have the drawback of requiring considerable force in order to be able to move the butterfly-type flow control element at the end of the closure movement and at the beginning of the opening movement.
In other valves, the gasket, instead of being fixed to the valve body, is fitted on the flow control element and protrudes from its perimeter.
With these valves, the annular gasket is much more exposed, with respect to the previously cited valves, to the action of the fluid that flows through the valve. The action of the fluid produces wear and deformation of the gasket, which can reduce the sealing effect of the gasket when the valve is closed.
In all of the above-described valves there is also the problem of separation of the annular gasket from the butterfly-type flow control element or from the valve body during closure and opening, since the movement of the flow control element produces a deformation of the annular gasket and fluid can seep between the annular gasket and the region of the valve body or of the flow control element to which the annular gasket is applied.
This seepage of fluid has the effect of causing separation of the annular gasket and therefore of reducing or even eliminating the sealing effect of the annular gasket.
The aim of the present invention is to solve the above-described problems, by providing a fluid control valve provided with an annular sealing gasket which is associated with the valve body and is designed to cooperate with the butterfly-type flow control element when it is moved into the closure position, and in which the possibility of separation of the annular gasket from the valve body is excluded with absolute safety.
Within this aim, an object of the invention is to provide a fluid control valve with a butterfly-type flow control element in which the presence of the annular gasket does not reduce excessively, in the open condition, the passage section available to the fluid.
Another object of the invention is to provide a fluid control valve with a butterfly-type flow control element which excludes the possibility of seepage of fluid between the annular gasket and the valve body.
Another object of the invention is to provide a fluid control valve with a butterfly-type flow control element in which the annular gasket is protected against excessive wear on the part of the butterfly-type flow control element and on the part of the fluid that flows through the valve.
This aim and these and other objects which will become better apparent hereinafter are achieved by a fluid control valve with a butterfly-type flow control element, comprising a valve body which is crossed by a passage with an inlet and an outlet which can be connected to two branches of a duct for a fluid to be controlled by means of the valve; said valve body accommodating, in an intermediate region of said passage, a butterfly-type flow control element which can be actuated in order to open or close said passage; said valve body supporting, in said intermediate region of the passage, an annular gasket which can be engaged by said flow control element in the closure position, characterized in that said valve body is provided in at least two parts which are mutually coupled at a region that is occupied by said annular gasket and lock said annular gasket between said parts in a mutual coupling position.